Phenolic Profile of Peanut By-products: Antioxidant Potential and Inhibition of Alpha-Glucosidase and Lipase Activities

Free, esterified, etherified and insoluble-bound phenolics from three samples, namely meal from whole peanuts (MWP), meal from dry-blanched peanuts (MDBP) and peanut skin (PS) were evaluated for their total phenolic content (TPC), and phenolic profile using HPLC-DAD-ESI-MSn. The TPC was in the order of PS > MWP > MDBP. Among 37 compounds identified 10 were reported for peanuts for the first time. Proanthocyanidins were detected in peanut skin and MWP, but not in MDBP. The presence of peanut skin in MWP rendered up to 9.8-fold higher scavenging activity towards the DPPH radical as compared with MDBP. Phenolics from all samples and fractions showed inhibition of alpha-glucosidase and lipase activities, which are key enzymes involved in the absorption of glucose and triacylglycerols, respectively. Therefore, their antioxidant properties as well as their potential role in the management of diabetes and obesity makes them worthy of further consideration as functional food ingredients.